Summary: Geophys. J. Int. (2007) 168, 27­39 doi: 10.1111/j.1365-246X.2006.03175.x
GJIGeomagnetism,rockmagnetismandpalaeomagnetism
Tests of core flow imaging methods with numerical dynamos
Hagay Amit,1 Peter Olson1
and Ulrich Christensen2
1Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
2Max-Planck-Institut f¨ur Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
Accepted 2006 August 4. Received 2006 April 26; in original form 2005 October 20
SUMMARY
We test the quality of a new core flow imaging method that incorporates constraints on flow
helicity, using synthetic magnetic secular variation data from 3-D self-consistent numerical
dynamo models. Comparison with the dynamo model flows reveals that our imaging method
delineates most of the main large-scale flow features, both in pattern and magnitude. The
dynamo model flows are characterized by high-latitude vortices, some equatorial symmetry,
columnar convection and a significant amount of flow along radial magnetic field contours.
Our inversion method correctly images these aspects of the flows. The correlation coefficient
between the dynamo velocity and the imaged velocity exceeds 0.5 in cases with large-scale
flow and magnetic field pattern, but degrades substantially in more complex cases when the
scale of the secular variation is small. The magnitude of the imaged velocity depends on the a
priori-assumed ratio of tangential divergence to radial vorticity k, in some resemblance to the